Improving paddy quality
There are numerous factors that determine the final quality of paddy produced at the farm. For best milling results, good quality paddy is needed and mixing of different varieties prior to milling should be avoided. The following factors are important in determining the final quality of paddy rice:
Prepare fields uniformly and as level as possible. Uniform water depth throughout the season will contribute to uniform crop establishment, uniform ripening across the field and, as a results. more consistent moisture content in the grain. Cut (i.e. lower) areas may mature sooner than fill (i.e. higher) areas of a field. Large differences in grain moisture content in rice contribute to fissuring and may accelerate grain spoilage.
Select the right seeding date and rate. Seeding date can affect conditions during maturation. High temperatures after flowering can lower the amylose content, increase chalkiness and increase gelatinization temperature. Higher seeding rates will lead to higher plant population, more competition for limited resources, and possibly more lodging and smaller grain size. Lower seeding rates will result in increased tillering with more variation in maturing within the panicle, and higher weed populations.
Ensure uniform crop nutrition across the field and apply nutrition in time. Uneven crop nutrition can lead to variation in tillering and tiller maturity across a field, resulting in highly variable grain moisture content at harvest. Nutrition can affect head rice and amylose content. Delayed nutrition may lead to delayed growth and crop maturing, which increases the probability that the crop is affected by adverse weather during harvesting season (typhoon, rain, etc.)
Keep a uniform water level on the field, and drain the field at the right time prior to harvest. If rice is exposed to drought stress, the rice plant will abort excess grains and fill fewer grains. Too early drainage prior to harvest may lead to incomplete grain filling and more misshapen kernels. Too late drainage prior to harvest may lead to inability to harvest rice at right moisture content due to field inaccessibility.
Check the field regularly for pests and control pests when necessary. Insects such as stink and rice bugs that attack the grain during soft or hard dough stages can result in deformed or spotty grains. The spotty grains arise from infection by bacteria transmitted during feeding. Stemborers cause whiteheads and thus add more unfilled grain to the harvested material. Late applications of pesticides may result in unacceptable pesticide residues in the grain.
Keep the fields free of weeds. Heavy weed infestations can reduce grain quality by out-competing the rice for resources (nutrients, sunlight), or by contaminating the rice with weed seeds with high moisture content. The latter can lead to transfer of moisture from wet to dry grain which promotes fissuring.
Harvest at the right grain moisture content and avoid delays in threshing and drying. Crops should be cut at 20-25% moisture content (MC) or when 80-85% of the grains are straw colored and the grains in the lower part of the panicle are in the hard doe stage. To avoid fissuring and excessive grain breakage, thresh and dry the grain as soon as possible after cutting. For combine harvesting or threshing with stationary machines, use correct machine settings to avoid mechanical grain damage.
Clean the grain after harvesting to improve milling output. The more impurities and unfilled grains are present in the paddy, the lower the milling recovery at the rice mill.
Dry paddy down to 14% moisture content. Overdrying (drying below 14% MC) can result in rewetting of grain in humid environments and subsequent grain fissuring and breakage. During the final stages of drying, the drying air temperature should not exceed 43% as higher temperatures will lead to fissuring. To avoid grain discoloration, do not store wet (undried) grain for extensive periods. For best results, the use of mechanical grain dryers for drying wet paddy is recommended.
Store the paddy at the right moisture content and protect it from insects, pests. The longer the grain needs to be stored, the lower the required grain MC. Seed stored at MC's higher than 14 % will experience growth of molds. Consider hermetic or sealed storage to reduce insect damage to stored grain.